This invention relates to a novel process for making pickled egg powder. More particularly, it relates to a process for making fragrant pickled egg powder which is rich in taste and has very little vinegary smell, and also to a process for making pickled egg powder excelling in digestibility and seldom inducing allergy to egg.
Conventionally, pickled egg is prepared by adding vinegar to raw, whole eggs, followed by 5 to 10 days"" pickling, and then served as food without any further processing. Whereas, not only many hours are required for its preparation, but also the pickled egg so formed has unfavorable taste and is unpalatable, impossible of preservation over a prolonged period and its servable time is limited. That is, heretofore practiced process comprises pouring vinegar into a container containing whole eggs, allowing the eggs to remain immersed in the vinegar for 5-10 days at room temperature to dissolve the egg shell in the vinegar and blending the solution containing the egg shell in the form of calcium and other mineral salts of acid together with the egg white and yolk in a mixer. The whole egg solution is served as health-maintaining drink in an amount of 10-20 ml per dose. Whereas, solubilized calcium and other minerals such as magnesium, potassium, aluminum, manganese, iron, selenium, zinc and the like in the form of acid salts are very bitter and furthermore acrid to the taste, and the solution is extremely unpalatable, in combination with the sour taste of the acid. Furthermore, the solution is occasionally liable to putrefy when kept for long, e.g., one to two months. Again, the pickled egg solution as formed contains various germs, but its sterilization by heating causes its coagulation (protein coagulation) and renders it unsuitable for a drink.
Pickled egg has been utilized as health food of old and various pickled egg-derived foods in which the above defects are improved, as well as their production processes, have been proposed in the past. Such proposals include, for example, pickled egg-derived food made by immersing raw eggs in citric acid or malic acid solution and after the egg shell is dissolved, stirring and mixing it with the egg white and yolk (JP Sho 55 (1980)-33B1); pickled egg prepared by dissolving egg shell in edible vinegar, adding white sesame seeds to the acid solution at a ratio of egg yolk cholesterol: linoleic acid=1:2 and mixing the same with a liquid of egg white and egg yolk (JP Sho 15 61 (1986)-158764A1); pickled egg-containing food in which the weight ratio of phosphorus to calcium is at least 2 (JP Sho 61 (1986)-234758A1); dissolving dry egg shell powder in edible vinegar and other organic acid solution, filtering, and mixing the filtrate with a solution of egg white and yolk (JP Sho 63 (1988)-45793B1); a process for making solid pickled egg by mixing dry egg white, dry egg yolk and egg shell powder with powder vinegar, organic acid and food seasonings (JP Sho 63 (1988)-47438B1); a pickled egg-like nourishing food which is made by dissolving egg shell powder in edible vinegar or an organic acid solution and drying the same to powder form (JP 25 Sho 61 (1986)-185168A1); a nourishing food and a process for making the same, comprising preparing pickled egg by immersing whole eggs or egg shell of birds in vinegar solution, on which occasion adding to the immersion system ascorbic acid and xcex2-carotene-containing foodstuff, adsorbing them onto maltose and freeze-drying the same (JP 30 Hei 8 (1996)-38107 A1); pickled egg, jelly containing ascorbic acid (JP Hei 8 (1996)-8017.iA1); pickled egg; jelly containing Ukkokei (Gallas gallus dometicus Brisson) extract (JP Hei 8 (1996)-80175A1); pickled egg food blend with dried mushrooms, parched soybean, dried sea tangle, Enmeis{overscore (o)} (Isodon Japonicus Hara), parched sesame seed, parched rice bran, Japanese persimmon leaves, etc. (JP Hei (1996)-214834A1) and defatted pickled egg power (JP 2707511) among others.
Those pickled egg-processed foods and their production processes heretofore disclosed did modify pickled egg-production steps, but the products invariably exhibit insufficient digestibility, are too strongly sour and bitter to be pleasant to palate and are liable to induce allergy to egg.
We have engaged in concentrative studies with the view to improve the bad taste of pickled eggs which were prepared by adding edible aqueous acid solutions to whole eggs, to now discover that very tasteful pickled egg powder can be obtained when a pickled egg solution which is made by adding edible aqueous acid solution to whole eggs is spray-dried under specific conditions, because excessive amount of the remaining edible acid is whereby evaporated off and removed, while the egg-constituting components are adequately roasted to emit fragrance.
We furthermore have carried out various investigations with the view to solubilize egg shells, which in their normal form have poor bioabsorbability, to a state easy of absorption as well as to improve the defects of pickled eggs which render them unsuitable for drink and to impart to all components of whole eggs inclusive of egg shell excellent bioabsorbability, and now discovered that concurrent use of enzymes capable of hydrolyzing protein, fat, carbohydrate, etc. in the occasion of solubilizing treatment of whole eggs with edible acids promotes decomposition (digestion) and solublization of whole egg components, shortens production time of pickled egg and at the same time the obtained pickled egg exhibits markedly improved digestive absorption and furthermore is inhibitory to occurrence of allergy to egg.
According to the first embodiment of the present invention, a process for making fragrant and tasteful pickled egg powder free of vinegary smell is provided, which comprises adding an aqueous solution of edible acid to whole eggs (including egg shell), at a rate of at least 150 ml of the solution per 100 g of the whole eggs, to pickle the eggs at temperatures of from about 0xc2x0 to about 50xc2x0 C., optionally filtering the resulting solution of pickled eggs, and thereafter spray-drying the same under the conditions of an inlet temperature of at least 180xc2x0 C. and an outlet temperature of at least 120xc2x0 C.
According to the second embodiment of the present invention, a process for making pickled egg powder is provided, which comprises adding an aqueous solution of edible acid and hydrolytic enzyme to whole eggs (including egg shell), carrying out the hydrolyzing treatment at from about 0xc2x0 to about 50xc2x0 C., optionally heat sterilizing and/or filtering the resultant hydrolyzate and drying the product to powder, preferably by spray-drying under the conditions of at an inlet temperature of at least 180xc2x0 C. and an outlet temperature of at least 120xc2x0 C.
Hereinafter the process of the present invention is explained in further details.
As eggs to be used as the starting material in the process of this invention, hen""s eggs (normal eggs, fertilized eggs, iodine eggs) are preferred, while eggs of other birds, for example, ducks and quails, may be similarly used. In the present invention, not only egg white and yolk but the total egg components including egg shell are used.
According to the first embodiment of the present invention, first whole eggs including egg shell are immersed in an aqueous solution of edible acid and dissolved. This dissolving treatment is conducted at temperatures ranging from about 0xc2x0 C. to about 50xc2x0 C., normally at room temperature and atmospheric pressure conditions, securing sufficient contact of all of the starting whole eggs with the edible aqueous acid solution. In said occasion, the system may suitably be stirred to expedite dissolution of egg shell. The immersing or pickling treatment is continued until at least the greatest part of the egg shell present is dissolved and solid shell component almost disappears, which normally requires 5-10 days.
According to the second embodiment of the present invention, the decomposition treatment of whole egg components can be conducted by adding an aqueous solution of edible acid and hydrolytic enzyme to whole eggs including egg shell. In that occasion, hydrolytic enzyme may be added to whole eggs together with the edible aqueous acid solution, or first the acid solution alone may be added to whole eggs to effect the decomposition treatment and at the stage where the egg shell is dissolved to a certain extent, for example, at a stage where the egg shell has been partially solubilized or after substantially complete dissolution of the egg shell, the solution can be optionally given a grinding treatment with, for example, a mixer, to form a ground emulsion, and a hydrolytic enzyme is added to the emulsion, followed by further decomposition treatment. It is also permissible, furthermore, to first grind whole eggs with, for example, a mixer to form a ground emulsion of whole eggs and then to add an edible aqueous acid solution and hydrolytic enzyme to the emulsion to effect its decomposition treatment.
The decomposition treatment is performed at temperatures ranging from about 0xc2x0 to about 50xc2x0 C., normally at room temperature and under atmospheric pressure conditions, in the manner securing full contact of the starting whole eggs with an aqueous solution of edible acid and hydrolytic enzyme. The treatment is continued until at least the greatest part of the egg shell present is dissolved and solid egg shell component substantially disappears. Preferably, it is continued for at least additional 1-2 days after the greatest part of the egg shell is dissolved.
The decomposition treatment time is freely variable depending on kind of starting eggs, their contacting conditions with the aqueous solution of edible acid, the decomposition treatment conditions, etc. Whereas, concurrent use of a hydrolytic enzyme renders it normally sufficient to pickle the eggs for 1-3 days. Thus, compared with 5-10 days"" pickling required when no hydrolytic enzyme is used, the treating time can be notably shortened.
Examples of aqueous solution of edible acids useful for the present invention include those of brewed or synthesized vinegar like rice vinegar, natural rice vinegar (kurozu) and apple vinegar; and those of edible organic acids such as acetic acid, malic acid, citric acid, succinic acid and lactic acid. They can be used either singly or in combination. These aqueous solutions generally have a pH ranging from 1 to 5, preferably 2 to 4.
The use rate of the aqueous solution of edible acid is not critical, but is variable depending on its composition, contacting state with whole eggs, presence or absence of hydrolytic enzyme, etc. For example, when the main component is an organic acid such as acetic acid, generally at least 100 ml, preferably 150-500 ml, inter alia, 200-400 ml of the solution per 100 g of whole eggs is conveniently used.
As hydrolytic enzymes which may be concurrently used with such aqueous solution of edible acid, various commercial enzymatic agents which are capable of hydrolyzing protein, fat and carbohydrate, etc. can be used. Specific examples include: Kreistase (Daiwa Chemical Co., Ltd.); Biodiastase, Newlase, Lipase and Pancreatin (products of Amano Pharmaceutical Co, Ltd.); Saccharated Pepsin (Mikuni Chemical Industries Co., Ltd.); and Lecitase 10L (Novo Nordisk Bioindustry Co., Ltd.). Use rate of these enzymatic agents also is not critical, but is variable depending on the kind of starting eggs and conditions of the decomposition treatment, while it is normally convenient to use them in the range of 0.01-1 g, in particular, 0.02 to 0.5 g, per 100 g of whole eggs.
Use of such an enzymatic agent promotes decomposition of the binder component constituted of protein, polysaccharide and the like, which is present between crystals of calcium carbonate which occupies at least about 93% of egg shell and other minor inorganic components such as magnesium carbonate, calcium phosphate, etc., to expedite water-solubilization of egg shell calcium with edible acid. Furthermore, decomposition of protein, lipid and glucide in egg white and yolk is also accelerated to reduce their molecular weights, whereby markedly improving their bioabsorbability. Consequently, the resulting liquid decomposition product of whole eggs has a number of valuable merits such that it does not coagulate under a heat treatment at 60-80xc2x0 C. which is necessary for sterilization, nor is it substantially denatured in the occasion of spray-drying.
The pickled egg solution or liquid decomposition product of whole eggs resulting from the above dissolution or decomposition treatment may optionally be heat-sterilized in accepted manner and/or given an enzyme-deactivating treatment and/or removed of residual solid component by filtration or like means, and then is dried to powder.
Drying and powderization of the liquid decomposition product in the second embodiment of the present invention can be carried out by any method known per se, e.g., spray-drying, freeze-drying or reduced pressure-drying, spray-drying being most convenient.
The spray-drying can be effected with an ordinary spray-drying apparatus. According to the first embodiment of the present invention, the characteristic feature of the spray-drying resides in that its operation conditions are specifically set to be at relatively high temperatures, such that the inlet temperature is at least 180xc2x0 C., preferably 190-230xc2x0 C., and the outlet temperature is at least 120xc2x0 C., preferably 120-170xc2x0 C., whereby excessively remaining edible acid, in particular, acetic acid, is removed by evaporation and pleasant fragrance is imparted to the egg components by the roasting effect achieved under the above spray-drying conditions, rendering the formed pickled egg powder extremely tasteful.
In the drying and powderization step, e.g., at the spray-drying stage, the pickled egg solution or the liquid whole egg decomposition product desirably has a pH value within the range of 5-8, in particular, 5.5-7. Where the pH value deviates from this range, it is desirable to bring it into the above-specified range, using an edible acid or alkali.
A more calcium-rich pickled egg powder can be obtained by adding such a calcium source, for example, as egg shell powder, calcium carbonate, calcium acetate or calcium lactate at an optional stage of the processes of this invention, in particular, the pickling and dissolution treatment of whole eggs in aqueous solution of edible acid or at the initial stage of the decomposition treatment with hydrolytic enzyme or before the drying step, to the solution or decomposition liquid of whole eggs. Generally adequate use rate of such a calcium source is, 1-10 g, in particular, 1-5 g, as calcium per 100 g of starting eggs.
Furthermore, it is possible and preferred to blend suitable excipient or additives in the occasion of spray-drying above pickled egg solution or drying and powderization of the liquid decomposition product. Examples of useful excipient or additives include, gelatin, collagen, casein, egg white albumin, gum arabic, tragacanth, starch, dextrin, sodium alginate, lactose, glucose, amylolysis product, skim milk powder, whole milk, soybean protein, soybean milk, vegetable oils and fats (cacao butter, coconut butter, etc.), animal oil (fish oil, etc.), vegetable extract, methylcellulose and carboxymethylcellulose. Also at least one of these materials serviceable as excipient may be used as a coating agent to coat the dry powder. The coating renders the pickled egg powder slow-releasing, to alleviate stimulation on mucous membrane of the mouth and still improves the taste. Furthermore, vitamins such as carotene, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, vitamin D, vitamin E, vitamin K1, vitamin K2, niacin and the like may be blended.
Besides the excipients, an emulsifying agent such as sucrose ester of acetic acid, glycerin ester of fatty acid, soybean lecithin, sorbitan ester of fatty acid and the like may also be blended.
The pickled egg powder which is obtained according to the above-described first embodiment of the present invention is free from the smell of residual edible acid, in particular, that of acetic acid, has pleasant aroma as it is adequately roasted, is very tasteful and excels in eatability and drinkability.
Again, in the solubilized whole egg components-containing powder which is obtained with the use of hydrolytic enzyme according to the second embodiment of the present invention, the egg shell calcium is made water-soluble, proteins in egg white and yolk are reduced in molecular weight and lipid as well as glucide also are decomposed, and in consequence their bioabsorbability is markedly improved. The powder furthermore richly contain various minerals, vitamins, saccharides, enzymes, amino acids and organic acids and excels in eatability and drinkability.
Thus the pickled egg powders provided by the processes of the present invention are highly useful as synthetic nourishment supply and nutritious foodstuff.
The pickled egg powder provided by the present invention can be processed into finished product upon addition of food additives such as flavering agents for foods, sweeteners, natural food colors and the like as necessity arises, and may be given a desired form such as powder, granule, flakes, capsules and the like. It can also be given a solid form by kneading with, or being dissolved in, for example, cooking oil (animal and vegetable oils), cacao butter, palm oil, white chocolate and the like and shaping. It can also be served as drinks and other drinkable formulations. It can furthermore be advantageously utilized as food-enriching additives.